As used herein, a “Carrier Network” generally refers to a computer network through which users (such as homes and businesses) communicate with various service providers. The Carrier Network extends from the location of each user to an intermediate switched/routed network (hereinafter “Intermediate Network”). The service providers, in turn, are connected to the Intermediate Network, either directly or indirectly via the Internet, for communications with the users. The Carrier Network is maintained by a “Carrier,” which also may serve as a service provider for certain services. For example, a Carrier or a related entity may serve as an Internet service provider (ISP). Two prevalent types of Carrier Networks include a “Shared Access Carrier Network,” in which data of multiple users are conveyed together over a shared communications medium between the users and the Intermediate Network, and a “Dedicated Connection Carrier Network,” in which data of each user are conveyed alone between the user and the Intermediate Network and are not combined with data of other users. One of the most prevalent Shared Access Carrier Networks today is found in the Data-Over-Cable (DOC) Network, which includes the traditional network constructed from coaxial cable and the hybrid fiber coaxial (HFC) network constructed with both fiber optical cabling and coaxial cable. Other Shared Access Carrier Networks include wireless and digital subscriber line (xDSL) networks (the xDSL lines typically being aggregated onto an oversubscribed backhaul trunk into the Intermediate Network, with the trunk defining the shared communications medium). When a user registers a cable modem to use a DOCSIS compliant network, a series of handshaking steps are executed during which the modem identifies itself, the network designates (among other parameters) the level of service and frequency (channel) that the cable modem may use.
After registration is complete, the cable modem (CM) will periodically or occasionally request the creation of service flows and, if allowed, the allocation of bandwidth to transmit data to a cable modem termination system (CMTS) in the upstream direction. The requests of CMs are granted by the CMTS that operates on any conventional methodology to determine how to allocate bandwidth on approximately a “per milli-second” basis. For example, with regard to DOC Networks, and with reference to FIG. 1 wherein a conventional DOC Network 40 is illustrated, data packets are transmitted in a downstream direction from CMTS 30, which is located in a headend 36 (or distribution hub) of a Carrier, over a coaxial cable 32 to respective CMs 34 of users. All of the CMs 34 are attached by the coaxial cable 32 to the CMTS 30 in an inverted tree configuration, and each CM 34 connected to the coaxial cable 32 listens to all broadcasts from the CMTS 30 transmitted through the coaxial cable 32 for data packets addressed to it, and ignores all other data packets addressed to other CMs 34.
The headend 36 in the DOC Network 40 includes a plurality of CMTSs, with each CMTS supporting multiple groups of CMs each connected together by a respective coaxial cable. Each such group of CMs connected to a CMTS defines a Shared Access Carrier Network, with the coaxial cable in each representing the shared communications medium. This arrangement of a group of CMs connected to a CMTS by a coaxial cable is referred to herein as a “Cable Network.” Accordingly, the DOC Network 40 includes a plurality of Cable Networks 38 originating from CMTSs at the headend 36 of the Carrier, with a particular Cable Network 38 being illustrated in an expanded view in FIG. 1.
The DOC Network 40 also includes multiple headends 36, 64, 66. Downstream data transmission typically occurs in a signal frequency range of 91 to 857 megahertz (MHz). This frequency range is divided into discrete channels each separated by a nominal channel spacing of 6 MHz. A cable modem tunes to an assigned channel and is theoretically capable of receiving data in the downstream direction with a maximum data rate of 30-40 megabits per second (Mbps). Upstream data transmission from the CMs 34 to the CMTS 30 typically occurs in a signal frequency range of 5 to 42 MHz. Data packets are transmitted in the upstream direction by the CMs at a frequency and modulation type (i.e., QPSK or QAM) specified by the CMTS. Upstream transmission employs a time division multiple access scheme and allows a maximum connection speed of 1.5 to 10 Mbps.
Many users typically share a channel and their interests compete for the bandwidth of the channel. The full bandwidth available to the multi-channel network for data transmission comprises the sum of bandwidths of the individual channels. A particular channel is congested when overcrowding occurs causing degraded performance to a user on that channel. A data packet typically waits in a CM buffer for an allocated time slot for transmission to the CMTS 30 on the assigned channel. A CM assigned to a congested channel can reach a full-buffer state, wherein data awaiting upload transmission fills the buffer. While the buffer is full, any new data for transmission to the CMTS, for example, data provided by a computer 44 for upload, may be dropped. In other words, the new data may be lost without being stored in a buffer and without being transmitted to the CMTS.
In contrast to the Shared Access Carrier Network, a user in the Dedicated Connection Carrier Network establishes a dedicated connection directly with the Intermediate Network for the transfer of data directly therebetween, and no data of other users travel over the dedicated connection. Examples of a dedicated connection are shown for comparison in FIG. 1 and include a connection established by a telephony modem 74 and a connection established by an ISDN modem 76. Both downstream and upstream connection speeds in a Dedicated Connection Carrier Network range from a maximum of 53 kbps in a telephony modem connection to a maximum of 128 kbps in a basic rate interface ISDN connection.
Connection speeds and, more importantly, throughput rate—the amount of data actually transmitted successfully in a given time interval—are important in minimizing downtime that users spend waiting for HTML documents to download from the Web. A Shared Access Carrier Network is considered superior to a comparable Dedicated Connection Carrier Network because the maximum instantaneous connection speed offered by the Shared Access Carrier Network is greater. A Shared Access Carrier Network is considered “comparable” to a Dedicated Connection Carrier Network where the entire bandwidth over a shared communications medium of the Shared Access Carrier Network equals an aggregate bandwidth that is divided between and dedicated to users in a Dedicated Connection Carrier Network. Accordingly, Shared Access Carrier Networks are able to offer significantly faster downloads of web documents, emails, and file transfers that are not considered available in Dedicated Connection Carrier Networks. Furthermore, new multimedia applications and Internet services, such as voice and video communications via the Internet, now are offered which require even greater throughput rates for acceptable levels of service than that of the traditional Internet services, i.e., throughput rates greater than that required for acceptable text-based Web browsing, file transferring, and email communication. It is believed that these new multimedia applications and Internet services cannot adequately be provided for over Dedicated Connection Carrier Networks and that, consequently, Shared Access Carrier Networks ultimately will prevail as the predominant type of Carrier Network for Internet access by users.
Of course, the actual throughput rates experienced by a particular user rarely, if ever, will equate to the maximum connection speeds of which the Shared Access Carrier Network is capable because of the shared nature of the communications medium. For example, in a Cable Network the total bandwidths available over the shared cable in the downstream and upstream directions, which determine the respective maximum connection speeds, must be shared among all of the users communicating at a given time. Thus, rarely will a single user have available for use a large portion of the entire bandwidth in a particular direction. Further, as a Carrier adds users to the Cable Network, the actual downstream and upstream bandwidths available to the user and thus throughput rates of the user generally will decrease. A Carrier therefore must be careful to draw a balance between the number of users connected to a Cable Network and the performance users experience communicating over the network.
Unfortunately, Shared Access Carrier Networks that have been established were designed to provide the traditional Internet services, and not the new multimedia applications and Internet services that require higher throughput rates for acceptable levels of service. Consequently, each balance previously struck by Carriers in establishing Shared Access Carrier Networks was based on considerations of the throughput rates required for the traditional Internet services, and user throughput rates currently experienced by users in such networks are believed to fall short of acceptable quality of service (QoS) standards believed required in a Carrier Network for the new multimedia applications and Internet services. Additionally, with regard to new Shared Access Carrier Networks that are being established, considerations of the new multimedia applications and Internet services tend to reduce the number of users that a Carrier now can reasonably expect to connect to the shared communications medium before degrading the performance levels of the new multimedia applications and Internet services. The balance is being shifted towards less users per shared access medium in exchange for higher throughput rates and, thus, higher QoS standards.
In an attempt to avoid reducing the number of users, it has been proposed, at least in DOC Networks, to discriminate between the traditional Internet services and the new multimedia applications and Internet services with regard to priority of data packet transmissions. In particular, the generally accepted standard in the United States governing communication protocols over cable is DOCSIS version 1.0, which was ratified by the International Telecommunication Union in March of 1998. DOCSIS stands for “Data Over Cable Service Interface Specifications.” When DOCSIS 1.0 was developed, it was generally believed that, in view of the “fast” connection speeds of Cable Networks, the provision of bandwidth on a best effort basis would be sufficient to meet all user requirements. DOCSIS 1.1 standards are detailed in Radio Frequency Interface Specification SP-RFIv1.1-109-020830, and DOCSIS 2.0 standards are detailed in Radio Frequency Interface Specification SP-RFIv2.0-103-021218, each of which is hereby each incorporated herein by reference and made a part hereof. These two specifications are available to the public from Cable Television Laboratories, Inc., 400 Centennial Parkway, Louisville, Colo. 80027-1266 USA, and may be available at <http://www.cablemodem.com/specifications>. Accordingly, each user subscribed to receive network access pursuant to a service level agreement (SLA) which provided for network access (or bandwidth in Cable Networks) only on a best effort basis. Now, in an effort to address the foreseen ever-increasing demand for higher throughput rates, DOCSIS version 1.1 has been proposed, in accordance with which each data packet transmitted over a DOC Network now must include a classification designation for prioritization purposes by network equipment. Subsequently, data packets representing voice or video, for example, now can be identified and given priority transmission over data packets representing email, file transfers, and text-based Web documents. A benefit of such flow classification is that, while overall bandwidth generally available to a user may otherwise remain unchanged, throughput rates of data for voice and video now may be provided at a higher rate than throughput rates of data for the traditional Internet services, thereby increasing the performance of voice and video applications and services while at least maintaining the traditional number of users connected to a Cable Network.
A disadvantage of the revisions to DOCSIS 1.1 is that the revisions do not enhance established Cable Networks constructed with only DOCSIS 1.0 compliant equipment, as such equipment does not support the added functionality of DOCSIS 1.1 so as to distinguish between data packets. More broadly, another disadvantage of the classification of data packets into Internet Protocol (IP) flows based on the services represented by the data packets is that such classification discriminates against users who do not utilize multimedia applications and services receiving the prioritized transmissions. At least for some extensive users of the traditional Internet services, some degradation in performance may be noticed by lower classification of their data packets, particularly if the user engages in, for example, web hosting. While the transmissions of data packets for documents, files, and emails are not as time-sensitive as data packets for voice and video, increased data packet latency for documents, files, and emails, even if incrementally small, nevertheless will result in service degradation for large or numerous documents, files, and emails.
Ultimately, a basic limitation of a cable network is that the separate interests of multiple users simultaneously compete for access to limited bandwidth on a shared medium. As a result, DOC networks are vulnerable to network congestion that can be causative of degradations in performance being experienced by the users. Improvements in bandwidth management are needed to combat the issue of congestion within existing cable networks. Accordingly, a need exists for a method and apparatus that will manage limited bandwidth on a shared medium by monitoring and dynamically allocating bandwidth according to predicted needs of both individual users and aggregates of users. The problems of network congestion may require solutions that outpace the computing time required in bandwidth-allocation software applications. Furthermore, needs exist for a method and apparatus for improved scheduling of bandwidth allocation on a channel used by multiple users. A need also exists for an improved method for making channel assignments to achieve load balancing among channels.